Just reading in blog(.)leadsquared(.)com/mobilegeddon-where-do-you-stand-a-month-after-the-roll-out/
What does the bold statement means?
Changes are crawled real-time
Even though April 21st was touted as a very important date, the crawling is real-time, so if you are for some reason, still not mobile-friendly, make the changes, and it would be crawled and updated as and when you update it, and resubmit for indexing, or whenever Google indexes it next.