Seems to me that on general principles, if you've got anything with less megapixels than a K-5, the K-1 even in crop mode will be superior, and that's before we get to the better AF, improved processing algorithms and all the other tweaks they put on the sensor.
If megapixels are all that matters (and they shouldn't be), a K-5 JUST beats a crop-mode K-1 - but all the other improvements would still be worth it.
A K3 or K3-II vs. the K-1 in crop mode would be another matter... but even then, the K-1 has more AF points in the crop zone and the AF system is a newer variant of SAFOX. There's a report someone posted on the forums a couple of days ago (ETA
here it is) about a German photographer who shot a circus with the K-1 all day long - fast-moving performers in low and shifting light with artificial fog - and was blown away by the camera's performance, and while I know it's only one user, it's the sort of anecdote I personally would pay a lot of attention to if I were considering shooting sports.
From what I've seen of the K-1 viewfinder overlay, if using a FF lens with crop mode activated you could use the periphery to anticipate the player's movements and start tracking them before they moved into the AF zone proper. Then you might hypothetically get a better focus lock earlier and a higher chance of keeping it.
The BIG question, OP, is how long you can afford to wait. I am forcing myself to sit on my hands for a year (unless I win the Ricoh Facebook competition, when I won't be waiting at all), because I don't need it all that badly, but even if I were as rich as Croesus and could buy it and all its lenses with my pocket change (so to speak), I'd wait a month or so until
unpaid and unsolicited reviews based on use of the production model came out.
If that circus photographer's report turns out to be an accurate reflection of the camera's performance, I think Pentax
might even have a world-beater on their hands. But I'm going to wait and see.