Q. Do you know when/if R.L. Allan will offer its ESV Reader's Edition in the updated ESV 2011 text?
Off the top of my head, I'm afraid not. Questions like this are best directed to the good folks at R. L. Allan themselves. My guess, based on past translation revisions, is that it will take some time to trickle down. In the case of the Reader's Edition, which is not based on a current Crossway/Collins text block, that may take longer.
The question you have to ask yourself is how important having the updated text is. The last time the ESV was updated, I recall getting questions about whether it would be better to wait before buying an ESV. After all, a quality Bible is a lifetime investment. You don't want to lock yourself into version 1.0 when there's a version 1.1 on the verge of being released. (This is the logic that has led me to hold onto my iPhone 3GS instead of upgrading to the iPhone 4 when I qualified to do so.)
In hindsight, the changes to the ESV weren't significant enough to make the wait worthwhile. And even if they had been, imagine holding out for the last revision before making that lifetime commitment, then getting the word that version 1.2 was coming down the pipeline. And suppose there's going to be a 2013 revision, too?
Obviously, you've got to decide for yourself whether the extent of the revision is sufficient to justify a new purchase. For what it's worth, it would take a major revision of English prose style (moving away from the RSVs more awkward locutions) before I could see myself "needing" to switch.