Georgetown Loop's schedule for 2015 has not yet been announced but will be posted here when they announce it:
[georgetownlooprr.com]
In 2010, Guanella Pass was closed all summer due to construction but I believe the construction is complete. Guanella pass and the Mt. Evans Highway are usually open by Memorial day if snow conditions permit.
The weekend after Memorial day would be more likely for the roads to be open.