It does indeed seem unwise to change all your HD timers at this point, based only on the speculation/predictions found in this thread. However, the information on channel 887 and in the Guide's programming descriptions for the English-language networks is official, "in writing" information from Bell, which suggests that one should go ahead and update your timers for those, and only those, specific channels. It also makes sense to frequently check that those changed timers are working properly during this transition period, and let Bell know if they screw up.
I personally haven't seen any of the officially-documented channels (i.e., the English-language networks) disappear from the 1000s since the phase 1 start date of Oct 14, but I only watch/record from a few of them, so I probably wouldn't have noticed. For what it's worth, my updated timers have been working properly since Wednesday, recording half a dozen shows from four of the channels in the 1000s.
Granted, Bell could definitely improve its communication, in particular telling us when the moved channels will disappear from the 800s, and whether our PVR timers will be updated automatically (like TiVo timers are) or need to be manually re-done.