True. I think Lucas can come back stronger. Think this team plus Lucas are top 4 material.
I'd have to say: this team+lucas+wide players -- then i'd agree with you about top4, or even better. It's not a good thing that we're so dependent on him, but then again, such a long injury as his is rare, and is not likely to happen again. With Lucas back, Gerrard hopefully injury-free, and Henderson and Shelvey both a year older, I predict a much more solid central midfield for us next season.
Only concern, as people say, is a defensive back-up; but if Lucas can remain fit, i don't see a problem in relying on Spearing for the odd game, as long as it's not any more than that. Money can be better spent elsewhere, e.g. wingers.