There probably will be a QVS v10 SR4, but you can never be sure.
Even QVS v9 will soon release another SR.
And considering there will always be a newer version at your fingertips, you could aswell use QVS v10 SR3, and upgrade to v10 SR4 as soon as it is released.
It is Always recommended to have the latest versions. As it has major fixes and bug corrections from previous versions.Right now the latest version for public release is V10 SR3.
The expected Date for SR4 is planned in nov 2011.
But it might change as per qliktech decision.
Hope it helps,
Got this from our Sales Rep. I did not know it existed and gives projected dates.
Our release mgmt policy is posted here: http://www.qlikview.com/us/services/support/product-upgrades
If you open up the pdf, it shows that QT is planning SR 4 in November and then there's also a plan for an SR 5 in May 2012.