I don't know if Phill said 5 more years but Lemmy always says he will do RNR until something really big stops him, so if Phill wants to retire, Lem shall employ some other guitar into MH, but I'd like to believe Phill will never quit.
Regarding the covers album, they should not cover metal because it isn't MH style, Rock & Roll more like it so I believe it will be more like a mix of classic twist with harder post 65' RNR eg: Chuck Berry, Buddy Holly, Eddie Cochran, L Richard, C Checker AND Led Zep, The Who, Deep Purple, Black Sabbath, T Rex.
Maybe some punk in too? Ramones, Dammed, Pistols.. Well hopefully
