> There is always a "backwards compatible" argument that pops up, but the solution is simple: persons that dont want to upgrade from their 2002 PHP installation can use legacy WP.

We tried a long-term support branch. It doesn't work with WP's development process, and it's a lot of extra effort. It's not too hard to maintain backwards compatibility on the other hand.

This means that legacy has to continue to be maintained for security issues. See Rails 2.3 (http://www.kalzumeus.com/2013/06/17/if-your-business-uses-ra...)

Correct. But the quicker you stop working with legacy code, the quicker the cutoff can be.

Even automotive manufacturers have to supply parts for cars they manufactured for X number of years after the final production. I hope new 2014 cars don't include parts from the 1940's era for "compatability" reasons.

I hope they do. There is an obscene amount of integral parts in automobiles that are made out of poorly formed plastics. Not only do a higher number of parts fail, the manufactures making replacements often follow the same flawed construction.

No 1940s vehicles didn't come with ABS, front and side panel air bags. But linkage in the suspension was at least metal, and wasn't known to fatigue every five years. If I were so inclined I could bring my hick mechanic in here and he would have volumes of corner cuts to cite that have resulted in unnecessary deaths over the years.

Some advancements have been great but overall legacy parts don't engulf vehicles in flames. Hodge-podge workarounds do[1].

[1] http://townhall-talk.edmunds.com/direct/view/.f0e40ac