The risks of downsizing are:
1. You are likely to regret selling a specific gun later when you regain in an interest in that gun or the type of shooting you would need that gun to do.
2. You might not be able to replace the gun in the future due to a change in the law.
3. The gun might still be legal to buy in the future, but you might not be able to find one for sale or might not be able to afford it if the prices go up.
Personally, I would advise against downsizing that drastically unless you absolutely have to.
Now, if there is a gun that you plain don't like, sure, get rid of it. That does happen and no reason to clutter up your safe with something you just don't enjoy shooting.
But, for the rest, you'll find your tastes and interests change and something that you are bored with now may be something you'll have great interest in the future when you "rediscover" that gun or type of shooting.
Here's another thought: Instead of "downsizing" have you thought of "upgrading?"
If you were going the "quanitity over quality" route you could start buying higher end guns that fill specific niches and sell off your current lower end guns to fund the new purchases. You'd wind up with fewer guns of better quality.
I'm talking about replacing a SKS and a WASR AK with a single good AR or replacing a Maverick 88 with a Mossberg 500. That sort of thing.
Obviously, if you already have higher end guns that doesn't apply to you, but since I don't know what kind of guns you have, I thought I'd make the suggestion.
One last thought: If you do decide to go to "just one gun" you still should *two* of that gun. A spare is a *very* nice thing to have.