As a club we rarely 'promote' players squad numbers, they tend to stick to their original designation.
Riise and Gerrard moving from 18 and 17 to 6 and 8 in 2004 is the last time I can remember a player changing numbers to a 1-11 (or did Maxi do it, I can't remember). Anyway it's not very common,
Skrtel, Lucas, Reina, Carra, Alonso, Masch were/have been all at the club for years were key players and all kept their higher squad number.
Sturridge should have been given 9 last year no doubt, Sterling 7 or 11 but we either don't do that type of thing or our players are weirdly loyal and superstitious