I think rails will stick around because they provide a vital functionality. It allows the user to have a weapon light and/or a laser mounted.
Holding a flashlight in your free hand and your firearm in your strong hand has some strong disadvantages. One, you are out of hands. This limits your ability to engage in other activities you need your hands for such as holding the phone/calling the police, opening doors, and engaging in a close quarter confrontation. That last one, may or may not require a free hand, but there could be an instance where the perp manages to jump out and grab hold of your gun, alternatively its conceivable that the perp poses a sufficiently limited risk that you may chose to use less than lethal force in dealing with them (i.e. 11 year old, unarmed gang banger). Secondly, you have to consider the design of your flashlight. I have one (non-gun light) which has a depress for momentary/press for on switch. I find the switch a little tight for turning it on in the continuous mode. Another switch system that I have seen uses a depress for momentary/turn for continuous switch. Turning the dial with only one hand (while holding the flashlight between your ring and middle finger - to allow some off-hand support for your weapon) is near impossible. Lastly, there is an increase likelihood of dropping your light. That can be pretty bad. Imagine it falling downstairs while you are at the top.
Not using a flashlight is also not a great idea. Sure sometimes it'll work, but not always, particularly not if you have to move around your house. If your house is totally dark, and you use no light, then there is a chance that you will stumble on the BG and give him a chance to wrestle your weapon away. Sure you have the advantage moving - your know your house and they don't, so they are more likely to bump into stuff. But that is reversed if they hold their position and listen to your footsteps. (This may be less of an issue if they are downstairs and you have an accessible phone upstairs).
Most houses are not perfectly dark, however. In fact there is often enough light from the clocks on various appliances, moonlight, street light in urban situations, and other external lighting such as your own motion activated lights to allow a person to be silhouetted while moving in front of a window or light colored wall. That once again mean that if the BG stops while you are moving he has an advantage. Even if he moves close enough to you to dash/shoot at you while you move towards the phone, the moment you continue your motion while he is stopped he has the advantage.
You could turn on the lights, but that creates the same problems. If you close your door and wait for the cops to show (assuming you have a phone in your room), the BGs can either make out with your belongings, with you being useless as a witness, or bust into your room. In that situation neither party will have a light advantage. If you are mobile during the incident whether its to investigate a bump in the night, to access a phone, or to engage the target, you are likely to give the advantage to the BG once you turn on the light. Most switches are in the same room/hallway as the lights which they turn on. So when you turn one on you are at least somewhat illuminated, but the perp may be difficult to make out in a less lit area. Also, in houses with an open floor plan, when you are in an illuminated area coming around a corner into a less illuminated area, your shadow will often fall on a wall visible from the less illuminated area. Similarly, the windows in an illuminated area serve as mirrors that can be viewed from nearby rooms/hallways. So if you turn on interior lighting you can be observed indirectly and give the advantage to the BG.
That leaves the option of having a light on your weapon. Gunutery is right in that they can be used to target you. However, running down an alley with your light on, and moving inside your own house are two different things.
In an alley there may still be shadows in which it is difficult to make out an individual & and a person may be outside the range of your light. In your own house the longest straight line is unlikely to be more than 40 - 50 feet and thanks to the walls & ceilings a good weapons light (typically in the 120 lumen range) will illuminate the entire space well enough. That means that if you turn the light on at corners, staying partially concealed behind corners, doors, etc to avoid presenting a silhouette, the BG will see you once you turn on your light. You will see the BG once you turn your light and scan the area - around the kitchen counter, the door way at the back, etc. So that gives the BG(s) an advantage of only a fraction of a second, and that may be partially offset by the dazzling effect of your light. We will assume that you and the BG have a similar reaction time. So the critical aspect will be who has the better accuracy. If the BG fires first, he may only have a general direction as a reference due to the dazzling effect of the light and lack of any clear visibility beyond the light. You will have the advantages of not being dazzled and using your sights. This would stack the odds more or less evenly. Doing down a hallway, where there is only one direction to focus on, you may even have a slight advantage.
Additionally, there are the benefits of a laser which may be mounted on your gun, even in the absence of a light. These advantages partially carry over to the daytime.
I think that a traditional, steal gun such as a 1911 looks nice without rails. However, firearms such as Glocks which are "boxy", for lack of a better word, around the slide, look better with a rail rather than a curved frame. At least that's my take on it. So in terms of aesthetics, its a toss up. It depends on the gun. But when practicality is factored in, rails offer strong benefits that should not be overlooked.