I think everyone was sad to see Bobby be sent off into the hereafter, but the actor that plays him certainly won't be struggling for parts. Jim Beaver is a veteran actor even though you may not recognize him without that trademark Bobby beard and hat. There's always a chance that Beaver will be returning occasionally to play Bobby either in a spiritual or angelic form or in flashbacks, but don't count on it very often. The producers are making a point to show the Winchesters as alone in the world.
Anyone needing a Beaver fix, keep your mind out of the gutter folks, can catch him on the television show Justified on FX with a semi regular role as Sheriff Shelby. The series follows Timothy Olyphant as as lawman with a 19th century attitude in a small 21th century town. If you like modern day westerns, then you may enjoy this.
On the other end of the spectrum, Beaver has secured at least two appearances in the final season of the AMC televisions show Breaking Bad. This has been a critically acclaimed show for several years and Beaver will be making a appearance during its swan song season. It follows the exploits of a terminally ill school teacher who in desperation begins working in the methamphetamine trade.
It's definitely a gritty show and closer to the emotional feel of Supernatural. Don't cry for Jim Beaver. Bobby may be gone, but you'll still be able to see him on television and possibly the movies.