Given that all three of them rarely played in the 2nd half of the season and that we have no midweek European games, I doubt we'll back fill them with signings.
For Suso, there's Teixeira coming through who will get the cup game minutes.
For Shelvey, he's already the odd man out in the couple of positions he plays - at CM, he's competing with Gerrard, Allen and Henderson; at AM / support striker, he's coming up against Coutinho and possibly Suarez. So these spots are already pretty crowded (with Teixeira also possibly playing here in cup games).
For Assaidi, there's Sterling and Borini at LF, and possibly Ibe in the cups as well; and Downing if we get an upgrade at RF which frees him to backup both LF and RF spots.
I'd think we'll be getting a player on the right who is ready to start and make a significant impact, pushing the likes of Downing out onto the bench. Or at least I hope to see that because that's an area we can really upgrade on, even with his improvement.
If Gerrard's fit, Henderson and Allen may even have a fair bit of bench time for a start, as I can see us playing with Sturridge, Coutinho, Suarez, <new RF> backed up by Gerrard and Lucas behind them. So I think we'll see a bench like: Jones, Kelly, Skrtel / Wisdom, Allen, Henderson, Sterling, Borini in the league.