I think this is possible, but, as noted in the comments above, simply executing y + 1 will not give the correct results, since this revision may be in a different branch. So, to find out what you need, the next version after y, you need to use "svn log".
Suppose you are in your workspace (above), which is completely updated. I ran this example in my repository and I selected rev 5402 as rev of my last build, this command gave me the range of fixes you wanted:
$ svn log -rHEAD:5402 | perl -ne '/^r(\d+) / and push @a, $1; END {print $a[0],":",$a[$
5531:5423
, , , , rev 5402, rev (HEAD, ), rev ( rev 5402). , 20 .
, , ( , x == y), , .