Castrovince speculates (note: not a rumor) about Marte's future with the Tribe in his latest mailbag:

The Indians have some roster moves approaching with the impending returns of Joe Borowski, Jake Westbrook and Shin-Soo Choo from the disabled list. If Marte survives all those moves, I'd be shocked.
...
I suspect the Tribe will go with five outfielders when Choo arrives (his rehab assignment will end June 3). That's why I made the above remark about Marte's tenuous spot on this roster.