I’m afraid, that nothing happend within last year even with new Stalker version. In my opinion, powering XBee via D5 is the designer’ wish only …
For my project (remote Stalker with temperature sensor and XBee powered by Lipol accu recharged by solar panels) I took finally the ideas from book “Arduino Projects to Save The World” by Emery Premeaux with Brian Evans making some small wiring on Stalker PCB in order to put XBee asleep. Beside this I send also the uP into sleep mode in order to reduce the power consumption. Both uP and XBee are waken up by on-board RTC (as far as I have Stalker v2.0 with RX8025 RTC chip I had to also modify some pull-up resistors on v2.0 board). And … it works 
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If you you’ll put XBee on your Stalker into sleep, don’t forget to modify the “sleep settings” on your router/co-ordinator XBee(-s) 
… It can be also the nightmare, nevermind the reduction of power consumption from accu is significant and it is worth of your efforts … 
Have a nice day
Vladimir