I am a SharePoint Developer with +1 year experience mostly working on SharePoint 2007 but very little on SharePoint 2010, Now I got a choice to either learn SharePoint 2010 or start learning SharePoint 2013 and do its certifications when they are available but not sure what would be the best way to move forward.
As always the answer is it depends.
My main recommendation would be that you should learn the product that it's most likely to be able to work with.
SP 2013 is where all the hype is at the moment, but in most companies the use of it is still out in the future.
And from a developer point of view if you know the direction taken in SP 2013 then the difference between learning future proff SP 2010 or SP 2013 is that big if you have a SP 2007 background.
If you stay with SP2010 then my recommendation would be:
If you can pick and choose I'd recommend starting with SP2010 with the focus above and then continue to SP2013, for a long time it'll be an advantage for SP2013 developers with a SP2010/2007 background
My advice - start to learn SharePoint 2013. Most core elements of both products are the same. If you have experience with developing SharePoint 2013 solutions , then you are also capable of maintaining solutions of older versions.
When you start to develop on the new platform, you'll learn the new VS features for packaging, object models (server vs client), Business Connectivity Services and many other features ... a lot of these features are also available in SP 2010 (may or may not in a limited version). Roughly, if you gain experience in SP 2013, you will automatically gain experience in SP 2010 with the addition that you are learning some new features as well, which will give you an advantage.
Knowledge is power :)