Trimble 5700/5800 RTK System
"Non-operational" might not be the best term for it, because you'll still be able to get data out of it that can be useful. But, as I understand it (I don't have any 5700 receivers), if the firmware is older than a certain version the receiver will misinterpret the GPS week and report faulty date and time information. While this can be managed for post-processed data, it may be fatal for RTK work.
The UNAVCO site has some information that might be helpful.
Frame Surveying & Mapping
609 A Street
Davis, CA 95616
Never heard that. Trimble doesn't support either the 5700 or the 5800. You even have to search eBay for parts. The stuff worked thru the last GPS week change without any problems. It uses only the old satelites so I wouldn't expect them to be getting changed. The last GPS week adjustment only affected processing thru OPUS. There's alot of folks out there still using nonGNSS equipment not to mention navigation equipment, I'd think it'd raise alot problems if they couldn't determine location.
My Previous Company has 10-15 of these. They work fine for static work unless you need to work with IMUs from an aerial mapping platform that collect data in GNSS too.
RTK is ok too if you have your FCC license(most didn't) and it won't interfere with the VRS signals as those are cell phone tower based data streams.
Otherwise, the link JF provided gives the guidance on the firmware updates and the cost per unit to upgrade I was quoted at like 600 dollars(rounded) per unit at one time.
GPS week 2048 (a power of 2) is begins April 7, so if the receiver has a limited number of bits for the week this could be the magic end date for RTK. After that it would be like the 4000sse/ssi receivers that think the week should be less than 1024 and so require manual intervention to get static results.