Lithium batteries

I think these upcoming LiFePO4 technology 12 volt batteries in standard group sizes with built-in charge control so that they're direct drop-ins for lead acid batteries could be the perfect next generation of RV batteries - except for one aspect: I don't care about them being much lighter weight in the standard group sizes as compared to good old lead acid batteries - that's not important. What WOULD BE GREAT is - if they were way up in amp-hour ratings in the standard group sizes as compared to lead acid batteries.

Wouldn't it be fantastic to have an RV battery available with characteristics just like LiFeO4 that was, say, 200 amp hours in Group 31 size? What us RV'ers need, IMHO, is higher energly density per cubic inch in our batteries - not necessarily lighter weight! I'd love to have 400 amp hours of 12V deep cycle battery capacity in my RV mounted right in the same spot and taking up the same volume as my current 200 amp hours worth of deep cycle capacity as is contained in my two current 12V AGM RV batteries. Where in the world is the real high tech battery chemistry when you need it!! :h

..... Or alternatively ..... when are propane powererd fuel cells going to be ready for anywhere anytime noiseless battery charging in the RV world?