Btrieve is almost always backward compatible. So, as long as your btrieve apps didn't use "undocumented" features of the software & you didn't customize heavily, the chances of version 8 working are pretty good for most of your btrieve apps.
That said, macola hasn't tested 7.6.200 on v8 pvsw nor will they. If you have trouble, you are totally on your own. Pvsw will not support your apps, only the db manager.
If you want to transfer your legacy apps to mssql, you might find that they are not available in mssql or that no conversion utilities exist to move the data from btrieve to mssql. Then you are looking at doing your own data conversion, rekeying, etc.
Don't forget about knowledge sync that allows you to move info, update files, etc from one odbc db to another: it doesn't care if one is btrieve and another is mssql. It's reasonably priced, but would require some programming knowledge or expertise, or a deep familiarity with the dbs you are using.
If you move to mssql, be prepared for a hardware & training investment. A DBA is a must in an organization running multiple sql dbs that share information or require extensive reporting beyond the generic app.