The basic question here is a new copy or wait for perhaps a new design - an altogether different lens, that Pentax may or may not announce at some unknown time in the future. That is somewhat of the age old question. If it's a lens (i.e., design/focal length) that you need/want for some reason, then it becomes either exchanging for a new copy or repair issue. There are horror stories on both sides of the argument - and as observed, along with the never heard ones where everything turned out well either the first or second time around.
In my case, I needed the lens in a couple of weeks, enough time for either an exchange or repair. I also needed that specific lens as there were no other 8-16 lens designs available - it provided a very unique capability. I was going to go the exchange route, until I read a posting here on the forum about someone sending in both the body and lens and CRIS essentially zeroing the fine focus adjustment, and then calibrating and aligning the lens to the camera body. I decided to go the repair route. I might add that in my case with an ultra wide angle lens, there is a point where you need to ask yourself if your expectations are indeed reasonable or are just too high. In my situation, I thought that it was front focusing but at 8mm just how perfectly sharp are things going to actually be? I had applied the maximum 10 units of adjustment and it did get slightly better, so to CRIS it went, where they found that it was at least 45 units out of calibration. They zeroed the body's micro adjustment, aligned and calibrated the lens to the optical standard, and then made sure it was perfect on the body. I could not ask for anything more - and a couple weeks later the lens performed absolutely perfectly, when I went shooting a tall ship up close. Actually, I just remembered this recent post also....
So, if the OP does really want the 60-250 lens, I think taking the repair route (with perhaps sending his body along - call CRIS first), may yield a better result than trying the exchange. The design is known to render excellent / superior results. There have been very few complaints about the lens (other than it is expensive). Its one of the best lenses around - * lens and professional grade. The repair outcome should be extremely promising. It might take a couple of weeks, but the result should be a perfectly aligned and calibrated lens to the optical standard, and then tested to his body. In theory, that's about the best you can do. You can't expect anything more.
In terms of a completely different lens design/focal length question - that can only be answered by the OP. It comes down to if this is the best item to spend funds on for his particular need(s). Only he will be able to make that assessment.