MacRumors reported over the weekend that Apple Music and iTunes Match libraries can now manage libraries with up to 100,000 tracks:

Over the past couple of days, MacRumors has received several reports from users who have been able to upload music libraries of greater than 25,000 tracks to iTunes Match or Apple Music’s similar scan-and-match feature, and Macworld’s iTunes expert Kirk McElhearn has also noted a number of reports on his personal blog.
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Update 12:08 PM, December 6: Eddy Cue has confirmed to MacRumors that Apple has indeed “started rolling out support for 100k libraries.”

It has taken some time, and longer than expected, but those of you with iTunes Match or Apple Music and large music libraries can now upload up to 100,000 tracks to the services, up from the previous limit of 25,000. Eddy Cue, Apple’s Senior Vice President of Internet Software and Services, first mentioned on Twitter in late June that Apple was working to “get to 100k [tracks] for iOS 9”. Apple missed that deadline, but Cue subsequently told MacRumors that Apple was working on it and that he expected it would be released “before the end of the year” - and indeed it now has.