If the Consistory were held today, Benedict could name 13 new cardinal electors; if he waits till the end of August he could name 14, and if he goes into October he could appoint 17, maybe 18. That would be a sizeable class, and some significant reshaping could be accomplished by naming so many new cardinals at one time.
An interesting breakdown at that link.
Reason: There are currently 13 open places among the electors. Between now and April 11, 2011, there will be 11 more open places, at which point there will be 24 open places among the electors. The next cardinal-elector to turn 80 will not be until November, 2011.
With two dozen possible places to fill, the pope will be able to accommodate the Americans, the Italians, and everyone else. As well, he will put his definitive stamp on the body of cardinal-electors, creating one-fifth of that group in one act.
Consistory after that: Early to mid 2013. From mid-2011 to the end of 2012, about a dozen more cardinal-electors turn 80, and by mid-2013, it's over 20, again. Should Pope Benedict live that long (may it be so, please, God), he will have created around two-thirds of the cardinal electors.