Oil prices are one of reasons for this escalation. Azerbaijani regime needs to get people on their side during times of economic crisis. Then they need to go to war to recover some support.
Azerbaijan has been preparing for this all these years, of course. The dream of return is what justifies the regime to a large part. Azeris are, of course, much richer, due to oil, and they have been able to build up a serious military. That, of course, is what has pushed Armenia into Russian arms: they do not have much of a choice.
Eventually, Azeris will try the reconquest - there is almost no doubt of that. Remember: there are many thousands refugees all over the country, who will not let any Azeri regime to forget. Alievs have forged much of their legitimacy on the issue (the war was effectively lost before they came back to power). Some solution must be found that would allow Armenians to retain control over most important population centers but that would give enough to Azeris to declare a victory and to announce the issue resolved. Otherwise, eventually, the local Armenian population will be slaughtered - long term, Armenia is no match for Azerbaijan either economically or militarily, and Russia is unlikely to be around forever.