In the decision, the court said they were not but eventually will address text messages.
I wouldn't want to be the guy to make the bad case law. Unless you have very solid PC that the recent messages contain evidence, such as EXACTLY what happened in this case, I wouldn't venture there. You'll end up make bad caselaw for us all.
Shut the phone off, do a battery pull if possible, place the phone in a faraday bag (bag that blocks radio signals), and contact one of the regional labs, NESPIN, MSP, or the AG's office for guidance in getting a search warrant. If you have PC that there's evidence in there, you should have no problem getting a warrant. There are boiler-plate cell phone search warrants out there ( I have a VERY good one I can distribute to confirmed LEOs) that make this easy. Executing warrants on the phones is very easy, the text messages, call logs, contacts, etc comes back to you in an organized Excel spreadsheet. It's actually the easier route to go.
IMO, digital evidence needs to be addressed very soon by the MPTC in in-service and on the EOPS e-learning portal. Officers on the street need to know how to safeguard this sort of evidence due to the very real possibility of the data being remotely wiped. The data that's on the microSD cards can be recovered if deleted, but not the actual phone's internal memory chip. Once it's deleted, it's gone.
Note: some labs can not break through some of the screen locks. How to possibly get around it: during booking, "What's your password / pattern so I can shut your phone off for you". Then seize the phone and record the password / pattern, then secure it in a faraday bag and/or shut it off.