In the US and Canada there is no immediate regulatory expectation for manufacturers to update to new standards for existing devices. In fact, standards in the US and Canada have no legal status, they only have relevance at the time you make an application for 510(k), PMA or device licence.
In Europe the situation is different. Standards are tied in with the regulation. Most notified bodies expect manufacturers to update to new standards at the end of a transition period; although this is open to argument as to whether this is really necessary considering not very well known preliminary comments in the regulation (whereas statements).
UL's mark is a private mark as well as an NRTL/SCC mark. So there are two factors for UL to consider: their own private transition period, and also the date at which UL 60601-1:2003 will be withdrawn from the list of NRTL standards and CSA 22.1 601-1 from SCC standards. I believe there are no dates set yet for any of these actions.
The situation is so complicated that UL may be just taking a global view when providing the recommendation to use the 3rd edition, and to update older devices.