I read that Panasonic will definately be ensuring all their new models are able to play DVD-RAM (including the caddy) for the forseeable future. I suppose they need to do this to support the format.
It's likely that Samsung will do the same.
Phillips will of course be pushing DVD+RW, Pioneer offering the DVD-RW and Sony supporting both these two while developing blue-ray. These makes are therefore unlikely to ever be compatible with DVD-RAM.
Philips machines are already accepting dvd-r discs, as well as their dvd+r. Don't know if that's just finalised dvd-r discs though (which is a somewhat pointless claim then, as most palyers will play finalised dvd-r discs...)
However, dvd-RAM is part of the new dvd-multi format, which is what all players (except Sony & Philips) will be pushing from next year (allegedly).