Maybe not so bad?
From reading the TriMet info sheet...
1. The closures begin March '07. The .pdf makes it sound as if the bike path won't be closed in its entirety, but only partially. I have to infer from this that certain sections will be closed for certain periods of time during the construction period.
2. The alternate route is being constructed as a permanent bike route, so once the LRT construction is finished, there will be twice the bike capacity through this corridor. I haven't ridden 92nd for awhile, but it's not too bad. It was the alternate route while the bike bridge was being constructed over Powell (another MAJOR improvement!!!) There are bike lanes between Division and Powell. From there, it's narrower (unless TriMet is adding a shoulder - as I recall, there is right-of-way available through there, but was gravel last time I was there). The Metro BikeThere! map lists it as a "moderate" street in terms of traffic volume and speed.
3. Significant improvements will be made to the existing I-205 bike route.
So, overall, I think things will be better in the long run and it sounds like efforts are being made to maintain a safe corridor during the construction. Maybe I'll go ride out there this weekend and have a look-see and report back.