It could also mean that a couple of players are have progressed much more than expected, and the team no longer has such gaping holes.
Not very likely. But an intelligent front office would not make decisions sooner than they have to, based upon inadequate information.
Which young player has any realistic prospect of performing well enough above expectations to put this team in contention?
Are Soler or Baez going to pull a Pujols and force the team to call them up and then put in a season putting him in strong contention for the MVP?
One of the young arms in the minors going to break out like Wood did in '98?
Even If Jackson tears up AAA at Iowa, he is not going to be called up before the middle of the season after the changes the team made to his approach, because they want to see that it sticks.
There really are no possibilities for what you seem to be suggesting.
If the team is doing reasonably well in late July, it will be because some of the scrap heap pitchers, the marginal vet outfielders, Stewart, DeJesus or Soriano are doing better than is to be expected, and those are the kind of players you move for prospects if you get a chance.
This is a team which was constructed to be mid-season sellers, not mid-season buyers.
Also, it doesn't seem impossible to add a couple of short term pieces without meaningfully sacrificing long range plans.
It's also possible the movie "Angles in the Outfield" was a documentary.
Even if short term pieces could be added without meaningfully sacrificing long term plans, something would have to be trades, and that "something" would be other than "plans." It would be promising prospects. And the pieces added would would be short term pieces marginally improving a team which would only marginally improve its chance of reaching the playoffs when it really would not belong... and they would come at the opportunity cost of trading established players on the Cubs who offer the potential for real help in the future.
The decision on trades in July will not simply be a matter of who is given up in the Cub system or who is acquired, but also a matter of what opportunities the Cubs would be giving up, what Vizcaino or Villanueva the team would not get if it was foolishly buying instead of wisely selling.
At some point the Cubs will certainly have improved to the point that short term and long term goals can be pursued at the same time, and even to the point that they need to be pursued at the same time.
They are not close to that point yet.