Yes, I think someone should do it, and yes I would do my best to support it as a fan and as a writer (not that I am in Ari's league, but just offering). However, I do think money and position in the magazine marketplace are factors. Maybe someone like GR could pull one together with the aid of Adamant and other major PDF publishers but somehow I doubt it.
Instead I see one company that has the magazine market presense and the money to do it: Wizards Entertainment. Not WotC, but the publisher of Wizards, Inquest, ToyFare, etc. Given that they cover most of the collectible/fanboyish market with one or more of their publications I will be a bit suprised if we didn't hear that they intend to try and fill the hole left by Dragon's absence. And it is Dragon that will be missed, IMO, Dungeon's content is too easily replaced by things like Pathfinder, DCC, and other print and pdf adventures.
Ideally? I'd like to see someone like Gareth, someone that knows the industry and publishing in it, linked to a company like Wizards Entertainment to produce a new Fantasy RPG magazine. Use the OGL to provide d20 Content primarilly, but also include other systems that either are also open or provided their content for the sake of exposure. You could easily feature one "genre" article each issue such as modern, western, supers, espionage, etc gaming that fell outside of the focus of traditional fantasy gaming. Have a regular column that deals with other types of games as well, reviews, industry news, and maybe an editorial or two by industry proffesionals and you are good to go. Comics might be OK, but not in abundance, and I would stay away from fiction in all but the most exceptional of circumstances.