If the Bears goal this season is to be mediocre and not be in playoff contention then they should just sit tight with their 4 DEs they have now. And I'm not sure that the 2 DEs they acquired (Walker and Raheem Green) are true DEs.
Gipson might increase his sack totals in his contract year. Robinson could take a big step his sophmore season. The new DTs could open things up for the edge guys.
But if you want to really improve this team you got to bring in some kind of talent on the edge. Hopefully, Poles has a plan and is playing chicken with a couple of these veteran FA DEs or is hoping someone gets cut. You can't have a team where everyone is 22 to 27 years old. You might need to sprinkle in some 30+ guys that can give you some quality snaps especially on defense where rotating is more prevalent.