I mean, i see 3 ways things can go this summer:
1. The status quo. Essentially, no outside goalie is added to the top 3, we go into the season with UPL, Comrie, and Levi. This feels like the most likely and the worst case scenario as its almost all involved. It immediately ratchets up the pressure on Levi as he's almost the default starter and neither UPL or Levi have anyone other than the coaches to help them learn to be a NHL goalie.
2. Bring in veteran, Comrie out, UPL/Levi fight it out for tandem role. This probably is a bit tilted towards UPL winning simply because Levi won't have to pass thru waivers.
3. Bring in veteran, UPL moved, one of Comrie/Levi rochester bound. This is probably more towards Levi being in the NHL as Comrie would likely pass waivers.
I think a lot of this probably depends on "Will the team ever be comfortable with a UPL/Levi tandem"
From a pure asset management point of view, I think you if you can add basically do an inplace upgrade of Comrie to a veteran starter who can be relied on for 40-50 games, that is the best route. You aren't losing UPL for pennies on the dollar, I think you take the pressure off of Levi as he doesn't have to be the starter next year, and you (probably) get the best immediate results.
There is the risk, of course, that UPL sucks it up at camp, Levi is good, and you are exposing UPL to waivers next. year.