Lots of good advice already
I've been in a similar situation to you, so thought I'd give my 2p.
Firstly, don't wait around for your dream game** ; enjoy playing/owning another game/other games.
I've been waiting about 2 years now for my dream game to come up for sale/trade and no dice ** in the mean time I've got to enjoy I think 5 different games at home now (only have space/cash for one at a time - current lodger Hallowen CE), which wouldn't have happened if I'd just waited around.
I'll admit, I went though times where I'd get a little stressed thinking I'd be gutted if my dream pin came up and I couldn't jump on it fast because I'd have to shift my current game , but that's still better than having no machine for an indeterminate time (or waiting a year+ for a new release)
As others have said, defo play whatever you buy first to make sure you like it (STh is great with thr UV Kit - would like one myself) - if you get something, you could always move it on when PF comes out, or if a STh vault happens)
**must include a caveat here

my dream game is of the premium/LE variety. As my first pin I bought a PRO ver. of that game which came up and loved it, but sod's law a Premium at a steal price came up about a month after I'd bought it, then I missed out on I think a further 1 or 2 I think during the subsequent year (and 2 LE's, but that's a bit irrelevant- no money for an LE at thr time as wedding/honeymoon to pay for) - now none come up

- tried putting out various wanted adds (but like STh there's a rumour of a vault/remake)
I'd still recommend (a) put a wanted ad up for a STh, then if no luck (b) enjoy some other games while you wait for a STh or PF (or something else yet to be announced!...)
As long as you get something decent, you can usually move it on fairly quickly of you need to.