Ok, I suppose that newer versions would be free too and the features will not be changed. Several applications change their features after a small free-period. Some examples? MailWasher, ZoneAlarm, AVG (See forum http://www.avast.com/forum/index.php?board=1;action=display;threadid=663).
The user is picked in a trap: use the program, like it and then it becomes Shareware…
By now, no other antivirus is so good as avast. I hope it wil be free in the future 8).