In addition to preview announcement of CICS/TS 4.1, IBM has announced that the end of support for CICS/TS 2.3 effective September, 2009.
CICS/TS 2.2 went out of support last April, and CICS/TS 1.3 went out of support in 2006. No dates have been announced for CICS/TS 3.1 or 3.2, but recent history indicates that CICS releases typically go out of support in 5-6 years. So, CICS/TS 3.1 should be good through the rest of next year, and 3.2 may be supported until sometime in 2013. If you believe in the Mayan calendar prophecy, CICS/TS 3.2 may be all you need – but what CICS release you are running is probably the least of your worries if you give that any credence.
If you are running anything older than CICS/TS 3.1, you need to decide whether to order 3.2 now, or wait and order 4.1 when it is available. There are typically price increases with new versions, so ordering 3.2 may be the way to go for the thrifty; if you want to get onto the latest and greatest (and have the capabilities to utilize the latest enhancements), or if you want to get on the release that would be supported farther out, 4.1 would be the way to go.