Lately I've been noticing a lot of cases where the successor to a given instance of web technology (specifically within the so-called "LAMP" stack of Linux, Apache, MySQL, and PHP/Perl/Python) isn't necessarily the next version of that instance, but rather something different. "Say what?" Let me explain with the specifics:

( Web Server: Apache 1.3 -> LightTPD )
( Programming Language: PHP4/Perl5 -> Ruby (On Rails) )
( Database Server: MySQL4 -> PostgreSQL ? )
( Operating System: Linux 2.4 -> FreeBSD ? Not much. )