There has been creation of new angelics but this was done long, long ago with the attrition in numbers represented by the fall itself. While the fallen ones had not disappeared, they were nonetheless not only unable to continue with their prior duties but became a threat in their own right and a burden to the other angelics who were called upon more and more to counter their negativity and effects on beings they manipulated. So this was dealt with long ago by readjusting things and indeed creating new angelic replacements to maintain the quorum needed to care for the universe in a planful and deliberate way. There is a process for taking care of such needs and this may well happen as the universe continues its expansion with more and more beings of all kinds coming online to be launched into new worlds.
This, too, will happen once the humans ascend, as they will be spreading throughout the universe and fostering creation of new worlds of their design, all of which will need angelic support and large numbers to do so. This will be fully supported by Creator. This does not mean to say the new worlds will only get raw beginners, this has been anticipated and in fact there is an increased angelic presence poised and waiting to assist fully with that eventuality. If there is no ascension, this will slow things down but the relaunch of humans back through the same track as the prior attempts will continue to burden the angelic realm heavily and the angels who are newer arrivals will continue learning all through the subsequent learning phase for the new round of divine human. So, there is a plan in place to deal with any contingency here.