Aircraft for XP12 slowly start to appear here and there. Some developers who stay close to vanilla X-Plane features (i.e. aircraft purely built with PlaneMaker and not or hardly using plugins, e.g. VSKYLABS) are mostly done converting their fleet. Light turboprops are a bit thin at the moment - only Thranda's Caravan so far, no PC-12, no King Air - but HotStart is working on their TBM, and TOGA will port the Mu-2 v2 in the months to come. Not sure about any King Air, AFL might upgrade theirs, but no official communication as of yet. Aerobask is (mostly) done converting their fleet (all Diamonds, but also their experimental jets and the Phenom).
Indeed it's a bit odd we see airliners of all sizes being ported, even the HS Challenger (maybe one of the most complex aircraft models ever built for XP, potentially any sim) has been ported, while there's hardly any GA (piston or light turboprop) available yet (Aerobask being the exception). Quite a few are in the pipeline - TS is working on their Cirrus aircraft and the Islander, and vFlyteAir has the Twin Comanche in beta test. JustFlight and Thranda both said that converting the JustFlight fleet would be the next big project of Thranda after having finished the Caravan (which has happened by now), so we might see some motion there as well. Also LES had announced the Sundowner would come "soon", but that was nearly 5 months ago.
That being said, so far we have more announcements than aircraft converted and ready to fly in XP12, and also XP12 itself is anything but mature. There are still a couple of issues Laminar has to solve (and yes, they're aware and working on it). I's say it's no mistake to wait until the end of the year, if stability is your primary goal. XP12 is really cool, but it's still mostly for early adopters who like to (or at least don't mind to) tinker with their sim.
Back to topic: I'm not biased about aircraft class and size, I love them all. While I have a thing for light turboprops (gimme a PC-12 in XP!), I mostly fly in XP12 these days, restricting me to aircraft available there. In the past week, I had a blast flying the Challenger from Shemya down to Fairmont in British Columbia, via Anchorage and Pasco, WA. I mostly fly in FSEconomy, so I just fly where the (virtual) jobs take me. And while the Challenger is a great aircraft, I can unfortunately only fly it on weekends - it's an intense aircraft, and performing a flight (including planning and preflight) takes its time - more than I can spare on normal work days throughout the week. On these I did a couple of milk runs with the Caravan, which is relatively quick to set up and get airborne.
For the summer I'm eagerly waiting for the LES DC-3 - this will be my go-to aircraft for my California routes in FSEconomy, with KNUQ serving as my hub.