Roundtable advise needed

I’m currently investigating the possibilities for improving the development workflow for a customer. What I encountered is kind of old, basically this:

-         Roundtable version is 9.1B

• The database runs under 9.1C
• OpenEdge version is 9.1D

-         The Roundtable connected databases are on 9.1D

-         The sites (of my customer) are running either 10.2A or 11.3.2

-         The test environments at the customer run the same version at the sites

-         RTB is not used to do schema updates at the sites (no clue why)

Recently they upgraded their last site away from 9.x.

Now, given the fact that moving away from 10.2A (or 11.3.2 for that matter) is not feasible on a short term, what would be advisable when it comes to a new Roundtable version?