I don't think we know the whole story. The NHLPA gave the salary cap, but probably asked for something in return.
I remember hearing that there are around 250 points to an average CB. You can probably remove half that are easy to agree upon or just stupid little details. That leaves you will about a 100 points to negotiate.
So, if they agreed to the salary cap right now, they'd just move to a different problem, and the NHLPA would want something in return for the cap, probably in regards to free agency.
Also, after signing the CBA, the teams would have to get organised, hire back all employees, sign free agents, bring players back, order equipement, etc.... So, that would take at least 7 days, maybe a bit more. Plus, the league would have to set up the schedule, organise charters, sell tickets, do the marketing.
Then, training camp and exhibition games. A few players haven;t been playing much and there would be a lot of players fighting for positions on teams. It would take at least a week of training camps and a week of exhibition games.
We're probably looking at a week for each stage, so they'd be starting in Mid March, which would be stupid and turn the season in a joke. It would probably just piss off most fans. So, I doubt anything will happen this year.