FLA batteries have been the standard for a very long time and have worked well. Now we have available AGM batteries that come with the same dimensions as the commonly used 6v golf cart batteries (I have 6 of those)that have a longer life and will accept a very fast charge although there is a higher cost. Those two options will cover the RV market well for a long time. Until those batteries demonstrate that they are a viable finantially practical option I can't see them finding their way into the RV market in any kind of a large scale.
Jim