AFAIK when the Tides come in the planned roster for the RFA would be 4 x Tides + 2 x Waves, presumably until the Waves have to bow out ~2030 (?) when it'll be down to 4 - expecting no replacement.
Considering the sort of use tankers are getting now, we might find it a bit tight. I again point to the RFTG in the Med, should technically have been deployed with organic tanker support but didn't.
Wave Knight is doing FOST duties (21/11/12), Wave Ruler is in the Gulf (9/10/12), Orangeleaf was doing FOST duties earlier in the year but no idea what now (27/4/12), Gold Rover is in the South Atlantic - assuming she's deployed as long as Black Rover was as there (~18 months) (21/09/11).
No Idea what Black Rover is doing either, in Sept last year she was due to get maintenance+ then do FOST duties when she got back from APT(S) but that's it, nothing newer than that. She's still listed as "Active - APT(S) which doesn't make sense, could be still in maintenance + take over from Wave Knight for FOST in the future?
Either way, lot of tasks being carried out by the RFA. a CVF might get topped up with FOST when leaving Portsmouth and maybe by the Gulf readiness tanker if she's in that theatre, but other than that she'll have no organic tanker support looking at the current numbers. We'll get some breathing space for the next decade (if the Waves can last another ~20yr) when the tankers become +1 than they are now but for a period after that we'll be -1.
The dates next to the operations of the tankers I gave above are from RN articles released on that date doing the deployment I listed, i'll be happy to post up links if it's required. But I dunno what Orangeleaf + Black Rover are currently up to given the information from the RN.