It may be worthwhile to have someone look up the support lifecycles for the operating systems used by various providers, if that information is available, as a means of predicting the versions which may be common at some point in the future. For instance, to use my previous example, it's likely that anyone using Ubuntu LTS releases on their servers will completely skip 5.4, but it's possible that their servers could continue running PHP 5.3 until 2017.
From a quick look around, though, such detailed information is rarely freely available, unless the hosting providers make it available on their own sites.
