I don't see why you don't think the Nets will stink for years into the future.
Quick list of the reasons:
1. Deron Williams, Joe Johnson, Brook Lopez all locked up for the near future.
That's part of the problem for _why_ they will likely have trouble staying competitive.
Johnson and D-Will will together account for $46M in guaranteed salary for 2015-16.
Lopez is not, contrary to your language, 'locked up' for that season, but instead has a player option for $16.7M. Assuming he stays healthy, he will almost certainly decline it UNLESS they extend him at a higher value. The reason is that he will be worth much more on the open market.
So, they will have a choice: Extend Lopez at around 20M, tying up around 66M on just those three players or trade him.
Even IF Lopez got the worst advice in the world from his agent and went ahead and played that season on his player option, they would be over the likely salary cap.
So if Lopez is still there, the only bodies they will be able to put around those three that season will be through resigning their own restricted and Bird-rights free agents, minimum contracts and the Mid-Level Exception contract (The Lesser, for tax-payers, likely). The only 'new blood' they will have added will be the worst of theirs or Atlanta's 2015 draft pick (because ATL has swap rights on THAT one as well as this coming 2014 one).
Now, they may go ahead and extend Lopez and just gut out that season, knowing that they would get salary relief the following year and could choose to build around Lopez.
But my guess is that they will probably look to trade Lopez before then to get rebuilding pieces (young players, draft picks). But if that happens, then that 2015-16 roster will consist of Johnson, D-Will and rebuilding scraps around them.
2. The Nets have all the money in the world, and no incentive to not continue spending it to field a competitive team. They have no picks so it's not like they can have a "bridge year" to try and replenish the talent on the team.
CBA rules beg to differ. All the money in the world doesn't matter. It can help you resign your Bird Rights FAs to big contracts to keep them. But it can't help you buy big external free agents unless you drop way under the cap. It can help you stay over the cap with trades ... but only up to the hard cap. And they won't have much to trade.
The Nets may or may not make much of a recovery this season, but the path back from desolation to mediocrity isn't so hard to see for them. Fire Kidd, sign some competent veterans on minimum deals, get a contributor for the mini-MLE, and have anything better than abysmal luck with injuries.
If they're really desperate, they can trade Deron or Lopez for a package of 3-4 role players in their twenties who can shore up the weak spots and keep them around .500.
Not sure why anyone would give up much for Deron Williams unless he proves he can stay at least a little healthy and play at a high level again. He's way too expensive. Unless someone shows up who needs 21M of cap relief in 2016 (last year before early termination option in 2017), who would trade anything for that contract?
And there no way anyone is going to want to eat Johnson's final 25M season.
Lopez is the only significant trading piece they have and the problem for them is that the timing of his player option puts them at a disadvantage.
It's certainly always possible to rebuild back to mediocrity from any point in the NBA - it just can take a few years.
But the 2015-2016 Nets roster looks right now like a train wreck about to happen.