Considering such a proposal would cut the Ku Band by nearly half in ITU Zone 1, expect the likes of SES Astra and Eutelsat to be strongly opposed to it, and you could probably throw in both Intelsat and Arabsat as well for good measure.
TBH, when it comes to finding new frequencies for mobile data/telephony where there is a proposal to reallocate frequencies that are already used to at least some regular degree (like Ku Band satellite downlinks), the onus needs to be shown that the terrestrial-based MNOs are already using all or most of their available bandwidth already before pressuring government representatives into asking the ITU to do things like this.
Personally, I'm still not convinced "5G" will be the killer technology that it is being hyped about at least at present, it reminds me somewhat of 3G (at least in the UK) where the hype surrounding it was about networks getting customers to make video calls at 50p per minute and to download video clips - when customers weren't prepared to pay ridiculous prices for the general novelty of video calling, and also finding out that Internet on their phones was nowhere near the same experience as on a PC (again with the not cheap costs) not to mention the poor battery life most 3G handsets had at the time (in an era when we weren't expected to charge our phones almost every night) as well as limited coverage on a frequency higher than that used for 2G GSM, it wasn't that surprising that it took quite a few years for technology to improve on several fronts as well as an improvement in coverage to really take advantage of its strengths that 2G couldn't offer. But by that time, 4G LTE was either just around the corner, or already there (in Norway & Sweden at least), with networks, governments and regulators having learned from most of 3G's mistakes (except to create a major new one - not baking in a VoLTE standard by default right from the start). I know 5G NR is designed at delivering faster speeds and lower latency compared to 4G LTE but in terms of general mobile use (i.e not fixed point access) what is there currently at present that essentially requires widespread 5G coverage that 4G, including advanced 4G features like carrier aggregation, cannot reliably do?