The only 50 cal that I personally know for sure that Tippmann is working on is the FT50 (not sure if that is what it will be called, but it's the 50 cal equivalent to the FT12). They are doing this with rental fields in mind because rental fields are screaming for a decent 50 cal rental. Currently I have more 50 cal players prebooked than 68 cal players (without promoting 50 cal) and all I have to give them is a Spyder Opus, which quite frankly sucks! I know there are lots of field owners waiting for this marker. I assume they will also have a retail version, but first and foremost, they are doing this for the rental market.
Since 50 cal will most likely be available at many fields in the next year or so, it makes sense for companies to pursue the magfed market with some 50 cal guns, in my opinion.