It all depends on what you are doing. If your interests are self-defense only, and not competing in the various kinds of matches (everything from IDPA, IPSC, to Cowboy Action, etc.), then you can get along with just a few guns. If you add match guns, then you are in trouble. If you want sort of a "reference collection" (one of several different types) you have another set of issues. You could, for example, get a well-known gun or three from each of the famous makers. Here is an example:
Beretta M9
Browning HP
Colt 1911A1, LE6920SOCOM
CZ75
Glock 17, 19, 26
HK45, P2000
Marlin 60, 336Y
Mossberg 590
Remington 870
Ruger MKIII 22 Auto, LC9, AR556, 10/22, 77 Gunsite Scout, American
S&W 642, 64, 617, 686, 629, Shield 9, M&P9, M&P9c, M&P22, 41, M&P15
Walther PPK, P99AS, PPQ, PPX
Do you see how this could get overwhelming?
On the other hand, if you are just interested in the simplest plan for defense, try this:
Get a pair and a spare of EACH (remember to buy additional for spouse and dependents):
Glock 26
Glock 19
Colt 6920SOCOM
ALWAYS have a 22 that will last a long time, such as Ruger MKIII 22 Auto, to allow practice with cheaper ammo
AND
at least a dozen magazines for EACH
AND
Spare parts
AND
AMMO, AMMO, AMMO
It sounds crazy, but in your scenario, you said you want to buy guns while you can, as you believe it will be illegal in a couple of decades. Under that scenario, you have to buy what you think you will need FOR LIFE. And, I don't know your life expectancy, but remember, magazines cannot be repaired, and ammo is like fuel - you use it up.