There's a lot of existing tech around, and there's a lot of tech coming on line very soon.
Mars one would likely use SpaceX falcon heavy(first flight this year) as the launcher and a modified dragon v2(flying by 2017, first tests this year) as the capsule.
There's also things like Bigelow inflatable habitats(alreafy tested twice in space, and another one due to be attached to the ISS this year) that would make a very good transport ship for going to mars.
As for rovers and a lot of other smaller things, nasa and private companies have been designing, building and testing things for decades.
It's more a matter of getting funding. Than technical, that's not to say it's not extremely hard.
I doubt mars open will get the funding, however it does serve a purpose, it raises public interest.
I think a joint international government and private company coalition is more likely to be first, but they won't achieve it as fast as they will need return capability even if it's not their main goal (spaceX)
Oh and mars one have already gone to several key suppliers to do a feasibility study, results of which as well as a actual substantial plan, Mars One are hoping to publicly release later this year.