The Players' Union is currently seeking an injunction in federal court to disallow the lockout imposed on the players by the league. In addition to that little fact that it will help decide if and when we have NFL games next year, as well as allowing free agency and trades, but also the decision that is made could very well dictate whether Sidney Rice is in purple and gold next year. Per the Washington Post:

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If that injunction request by the players is granted, the sport would reopen for business and the league would have to put work rules in place. Sources from throughout the sport on both sides of the dispute said over the weekend that the system the league would enact at that point would be very likely to be the same system that was in effect last season, when there was no salary cap in the final year of the just-expired labor agreement between the NFL and the players’ union.

That would mean there would be no player-payroll maximum or minimum for NFL teams. Players with expired contracts would need six years of NFL service time to be eligible for unrestricted free agency, rather than the four seasons required when the salary cap system was in effect; players with expired contracts and three to five seasons of NFL experience would be restricted free agents.

(emphasis mine)

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On March 2nd, the Vikings extended a restricted free agent tender to Rice, and he's a 4 year vet, so if the lockout injuction is granted and the upcoming NFL season is played under last year's rules, Rice will be a Restricted Free Agent and the Vikings will be able to retain him.

But if, on the other hand, the lockout is upheld, the union and the league will only be able to play next year if and when they agree to a new CBA, in which case in all likelyhood, a player will only need 4 years of service to become an unrestricted free agent,

So in short: lockout upheld, new CBA (eventually) agreed to = Sidey gone.

lockout lifted, no new CBA needed to play football = Sidney stays (for one more year).