Yes all FCA 767's will be in the new config. The change is NOT happening as smoothly as suggested however. AN is now at least 3 1/2 weeks overdue. That's not all bad in itself as the new config has not been 'sold' to the public for flights before May 1st.
Currently however many who should be flying long haul FCA routes are being flown via Canada on 757's whilst AN's refit overruns.
BL has been sold to the public for flights as of May 1st. Judging by the lateness of both BK and AN to date I don't think realistically it will make the UK in May at all!! Standby for chaos whilst it's flights are either operated on 757's or subbed out to a third party operator....... There is no option.
Which routes in May will be effected seem so far unannounced. If you happen to be on a FCA 767, then you'll love it, it really is very good, but the conversion project IS behind schedule and passengers will be effected for a good while yet :-(