I think Britney will be able to embark on a North American tour following her Vegas stint. Cher did her three year residency from 2008 - 2011 and then 3 years later she toured NA and sold out each show so far (given, she did do promo like The Voice and DWTS but still extremely impressive). I wouldn't put it past Britney either. Globally, I don't know how she'd fare but in the US, I see her doing well for a few more years.
Definitely would be best to do an album in 2015 to promote the last year of the residency and the residency will end in late 2016 (2014, 2015, 2016) and then in 2018 another album to promote a North American tour the following year.
She hasn't been this happy and successful in years. AND the universal praise from everyone is boosting her confidence 
