I think Arsenal need a good striker. If they can't sign a good striker, they can't stay strong in this race. Liverpool are in this race because of the personal skill of the manager Jurgen Klopp. When Jurgen Klopp leaves this team next season, they may never be in this race again. My assessment tells me that Manchester City are the only favorites.
January/Winter transfer window has been closed since 1st February, it will be impossible for Arsenal nor other clubs to bring new players after that date.
Regarding Liverpool - Its too early to say like that, Liverpool without Klopp doesnt mean Liverpool is not a strong team anymore, there are still many good coaches/manager whom able to replace Klopp.