WordPress doesn’t have any arbitrary limits.
You just have to make sure your infrastructure CAN support it… and it’s TUNED to support it both DURING and AFTER the import, especially if you envisage getting a large amount of traffic (I’ve seen Google bot alone killing little servers!).
You should also make sure whatever tool you’re using to do the import does the job in small batches to avoid timeouts, out-of-memory issues, and maxing out the CPU — all of which will crash the import.
For what its worth, the WordPress software is used on major news websites like TechCrunch, New Yorker, Variety, Quartz, TED, CNN, CBS, NBC, etc. Heck, WordPress.com, which runs WordPress under the hood (plus their own extra spices), see over 70 million *new* posts and 77 million *new* comments *each month.*
(I’ll assume, all these sites have far more stuff than yours, but we can also safely bet that they have some serious infrastructure and dedicated technical hands keeping the ship afloat, not some shared hosting account or an el-cheapo VPS)
Good luck!
