Sorry - I do not know about Vegas 11 - but I "upgraded" from Windows 7 to Windows 10 last week - and everything concerning my Vegas 12 and 13 - including plug-ins etc. - just survived through that process.
There were several other and quite surprising issues however - but after a couple of days Googling for ideas from other fellow sufferers I have just decided to keep Windows 10 on that machine.
On other machines (laptops) I had to revert back to Windows 7 as i.e. the ACPI's drivers managing the "blue labelled" function-keys (Volume up/down, etc) were not available in a Windows 10 version for these 3-4 years old machines.
Vegas Pro 13 is Windows 10 compatible however the previous versions are not fully supported on Windows 10. That being said most users of previous versions are able to run them on Windows 10 without experiencing issues.
We recommend doing a reinstall if you experience issues launching Vegas after doing an in place upgrade from Windows 7/8 to Windows 10. If you are not experiencing issues after the upgrade, no need to do a reinstall.