A lively & engaging read - good work by both Jeff and Kevin!

[ Jeff ] Where would you like to see WordPress 5 years from now?

[Kevin] I like the fact that WordPress has started removing things like blogrolls and adding them back as plugins. The core version should not be too bloated.

The problem is that there is so much functionality lacking from the core that you end up installing lots of plugins, thereby slowing down your site.
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Today, I have over a dozen plugins that I install on every website. I review the plugins I have installed regularly, though a quick check on my personal blog shows that I have 37 activated plugins. Many of these plugins address problems with other plugins or problems with the core.

It is a little shocking & disturbing (and portentously telling, too, tho telling what, we remain unsure), that as few as a dozen or 37 plugins might casually be regarded as - yeah duh - obviously flirting with "slowing down your site".

You cannot make your WordPress site 'all that it can be'; you cannot enhance and customize it freely with plugins, because the overhead posed by larger numbers of plugins becomes too excessive, too quickly.

This situation renders some of the implied promise of WordPress - putting it sympathetically - Unobtainium.

The recent/current flap over inclusion of a Post Formats UI in core for WP-v3.6 (actually, this appears to be something larger/weightier than a 'flap') raises questions about the real intentions & goals at the Head Office. Is it going to be a sleek core, and a virtually limitless array of plugin-functionality?

Or is it indeed going to be creeping bloat in the core, and 25,000 (who doubts 50,000??) plugins, from which you are free to make use of only a handful, lest your site should slow to a crawl, and your hosting provider scare you with communiques about "excessive resource usage"?
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In fact, it is quite possible to adopt various approaches to effecting a de facto "plugin compiler". This is usually not real compilation, but readily delivers similar advantages, particularly in terms of speed (time being the resource that hosting providers most-zealously monitor & guard!).

100-fold improvements are typical, which suggests that instead of regarding 30 to 50 plugins as fully-loaded, several thousand would perform as well, on the same platform.

In fact, sheer brute computing horsepower is a pragmatic, effective & affordable solution for gross & ridiculous computing inefficiency, and has been for many decades.

Instead of shared hosting, move to a dedicated server: you get your own computer & server, at the host's commercial farm. While this is rarely done for the everyday private blog, it is actually so cheap that realistically it is well within the range allocated to 'hobbies'. Folks will spend a lot more on a nice new Lycra bicycle-suit, or a new hunting rifle or pistol.
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WordPress will not have met the plugin-promise, until inventories of The Best 100, 200, 400 and 800 Plugin Ensembles are popular article-topics in the WP-literature.

Notice, that when talking about installations utilizing several hundred, and certainly when we talk thousands of plugins ... there are going to be outstanding opportunities for employment and commercialization. Merely knowing what the options are and how to deploy them in attractive forms for different purposes, will be valuable.