ouch. If I understand what you just communicated, you've got a site that had previously worked with the www version, but now, due to technical changes, the www version doesn't function? And won't for a couple months?
That's a scary scenario and having worked with many different developers and systems administrators over many years, I've never allowed one to tell me "we can't fix that for a couple months" and get away with that claim.
It can either be addressed or it can't at the site level or the server level, one way or another. Regardless of development framework, you should be able to set the non-www to redirect to the www version at the server level and it should work right. If there's a massive bug in the Magento implementation, that sounds like a very serious flaw in the developer's skill set as far as I can tell.
So - IF you're stuck, you're going to have a major SEO problem for longer than a couple months.
By all rights the only solution in that scenario is to scrap the www version altogether and NOT revert back to it in a couple months. Change all the 301 redirect settings and within GWT to now point to the non www version. Then work to build up more links to the non www version over time.
Because that's the only short-term solution you can do now from a best practices approach if the failure can't be quickly addressed.
And down the road, if you do this, you'd have to once again reverse everything, just causing you more problems.
So either get a developer / IT specialist who can fix it immediately, or scrap the www version altogether.