I am surprised to hear that Sony Ericsson would allow for T68m to be flashed into a T68i. It can totally keep two price tier on T68m and T68i. For example US$550 for T68i and US$450 for T68m. And I bet there will be people buying into both tiers.
But once it has allow for the flashing, we customers would benefit from it. So I say the price would probably be arround $350 - $450 for a while until May when the P800 comes out, at $600, I think.
*** Above are my own speculations only ***