Apparently, TakaraTomy are retiring the Masterpiece Optimus/Convoy mould, with one last release - MP-1L.

Probably very minor deco changes, like they did between MP1 and MP4, but the difference will be a sound-base will be added, which the Hasbro DVD Anniversary version had (and the JP 2010 Mail-away promotion).
It is said that the sound-base will have a message from the original Gen1 Convoy voice-actor (Genda Tessho) to announce the next Masterpiece figure.
Since this version has a tentative release date of March 2011 (two months after MP Rodimus), it should be revealing a brand new Masterpiece toy. (bring on Galvatron!!!)

On a side note - another production run of MP-5 Megatrons is coming soon as well, for those who haven't yet got one or don't want to pay hefty 2nd-hand pricing.