From the server side -- sure you can continue to patch/update your citrix apps etc.
If Google drops Chrome in 5 years time and in 5.5 years there is a massive flaw (some form of root-kit that saves every username/password and grants you access to the citrix system or the ceo's cloud based email account). If google decides that it wants to focus on Android and drops Chrome -- the pain could be immense. // This obviously doesn't apply for smaller faster moving companies.. But if you roll out 10,000+ Chrome systems -- Long Term Support plans are a good thing.
Otherwise - I agree. If you can replace a complex win/mac system with a cheap dumb chrome terminal -- the benefits for support are immense.