Very tough, now that I have 25 (or so) basses. I will assume you will let me keep my standup and EUB, and my travel bass.
1. 4-string Fender Precision - I'd probably keep my '64 Precision strung with TI flats, and sell the '74 and 2000's 4-strings and the 5-string
2. 5-string Sadowsky Ultra-Vintage Jazz - this is the most flexible bass I own, it can get all the sounds that the Precision doesn't work for.
3. 5-string Fodera Emperor Fretless - I love my Rob Allen and L2000, but this is the fretless I play the most and it can do just about anything, in a pinch it could sit in for a fretted bass to get a different tone.
What I'd miss:
Having a 4-string and 5-string version of different types of basses
Having a cheap but good version of vintage basses to take to bar gigs and on the road.
Basses that are not Precision or Jazz derived, like G&L L2000, Lakland Decade, semi-acoustics, ABG, etc.
Variety in tone and playability and strings and looks
What I wouldn't miss:
Buying new strings
Constant set-ups
Having to store and keep basses and cases
Not being able to spend enough time with each bass to know every nuance