I have about 6 Months until a Payment is Due to RoundcubeSkins.net. Going Back to Non Responsive web mail is Not an Option that I desire. About How Many Years until RC Next is Ready?
RoundCubeSkins.net (which gets themes from RoundCubePlus) are probably the best RoundCube Responsive-Design themes out there.
For the amount of time you spend on the alteration of your own RoundCube theme, getting RoundCubePlus.com themes are a great deal.
The response times of the designers are slow, but overall, the Themes are great. Highly recommended.