Takeout, Google's mass data migration tool, now lets users merge connections from multiple Google+ accounts. Standard Google users probably haven't created multiple profiles, but the news could come as a relief for users of business-based Google Apps, who often end up having a separate profile for corporate and personal use. The process is outlined on this help page, and while it's not too difficult, it will take a while: there's a seven-day waiting period, after which Google will take about 48 hours to transfer your connections.
During the transfer, neither account will be able to share content, add or remove users from circles, or block and ignore people. After it's done, anyone with either account in one of their circles will see the same profile. Unfortunately, comments and posts won't be transferred from the source account to the destination, so you'll want to back up anything you care about first.