It depends...
Do you have another full-sized auto? Do you have another concealable auto? Do you have a revolver for either of these roles (i.e. it wouldn't be as bad to be without one if you have a revolver that fits that role)? Do you have another 9mm?
Ammo considerations (in case you don't have another 9mm):
-Few options allow cheaper practice than 9mm
-9mm does have some very good defensive options
-.45ACP is more powerful in general and so you don't have to be as careful in your ammo selection
-.45ACP in a short barrel isn't at its best- if you get the PT145 M. Pro, stick with the 185gr loads and stay away from the heavy 230gr for defense (230gr JHPs probably won't expand). So you lose some of the prior advantage (i.e. in a short barrel .45 you now have the need to be more careful with your ammo selection, just like with 9mm).
If you don't have another full-sized auto I fully agree with the suggestion to wait and save until you can buy the PT145 M. Pro outright. They aren't that expensive. It may take a few months, or longer depending upon your income, but try to make due with the P95 (assuming you have no other carriable guns) in the meantime. The larger gun, especially in the inexpensive and light recoiling 9mm, is something that you will appreciate at the range.
How well do you like the P95? Trust me, you don't want to trade a gun you like for something else. If you don't like it that much (or are lukewarm) go ahead and trade, if you like it then make due until you can afford the PT145 outright.
Now if you don't have another concealable pistol and you have trouble concealing your P95 AND if you live in a CCW state and you have your CCW license, then it may be more valuable to trade now regardless of your above answers. However, even so, if you have some money you can afford to spend you may be better off buying something cheaper (a Kel tec P11, P3AT or P32, a used Taurus 85 revolver, a used S&W J-frame, etc) so you have something concealable now, keep your P95, and save for the PT145 that you want.