cosmonaut
Well-known
I have an a99 pre ordered and also a Leica 90mm 2.8 on the way. The 90mm will be my portrait lens. If you shop around you can find Leica R lenses at good prices. Since the a99 will have focus peaking it should be really easy to use.
To convert you just buy a new mounting ring for the lens and swap it out.

Summicron 50mm by Cosmonaut's, on Flickr
To convert you just buy a new mounting ring for the lens and swap it out.

Summicron 50mm by Cosmonaut's, on Flickr