I think the current Pentax lineup does not demand any high quality TC except maybe 1.4x for the DA*200/2.8 & DA*300/4 (both demand different designs like 1.4x-L & 1.4x-S). However, the problem is that the majority of existing Pentax users are asking for high grade affordable TC for their consumer zooms, which aren't good (too slow and not sharp enough) for TC to start with. The DA*50-135/2.8 might be the exception, which might or might not be sharp enough for TC. Personally, I feel there is no significant market for any Pentax pro grade TC, not until Pentax have some killer super-teles, which again won't sell in significant volume in the first place. If they repackaged the A1.4X-L for DA*200/2.8, it would eat away the sale of DA*300/4. That leaves only a DA 1.4X-S for the DA*300/4 which is really a little slow for TC in practice, and the DA*300/4 is not exactly popular either. That means it makes no sense for Pentax to produce any pro grade TC at all.