Elyounoussi signed up for a second season-long loan on Tuesday but Celtic fans have received far less positive news over the future of his Southampton team-mate Forster.
The goalkeeper rejuvenated his career at Parkhead last season but reports claim he is set to fight for his first-team place at St Mary's, where he has two years left on his contract.
However, Elyounoussi has not given up hope that the former Norwich keeper will sign for Celtic for a fifth time – having had two loan spells earlier in his career before moving in a permanent deal from Newcastle.
Elyounoussi said: "It would be great for us to have him here for another year obviously but we just have to wait and see what he decides to do.
"I have talked to him. He's not sure yet what he is going to do. Hopefully he comes back here."