[_joe]

Techops at WMF here: the TL;DR is "no", but I can get into details.

MediaWiki accounts for the lion's share of the servers we run (between MW itself and the databases and the object storage for files/images, I think around 60%), but it's not really that inefficient, also because we aggressively cache content on our own CDN.

Given the amount of traffic we handle, I don't think any sgnificant change could reduce the hosting burden much - and it's already a very small footprint at 2M/year. To give you some context, we have currently less than 2000 physical nodes across all of our datacenters; it's pretty hard to reduce that number further while guaranteeing stability and performance of the sites.

I'm not saying we couldn't improve things - there is always room for it - but I doubt we could do something that reduces our hardware footprint by a significant amount. As a benchmark, moving from PHP 5.x to HHVM gave us more capacity and over two years we reduced by 15% the number of MediaWiki application servers, but that does not result in a huge change in the hosting bill.