What drives new arenas is an innovation that makes the existing arena obsolete. Luxury suites are what drove the arena boom of the 90's. There's no new innovation that is making the current arenas obsolete. The only argument for a new arena for the Senators is that there's money to be made in a new location.
Saying there are only 6 rinks older, besides being flat out wrong, is a bit disingenuous when half the rinks in the league were built between 1994 and 1999. If age was an issue, half the teams in the league would be planning for a new rink.
Assen na yo!
Older Rinks
Climate Pledge Arena and MSG: underwent $1B+ renovations.
Calgary: new arena coming.
Honda Center in Anaheim: undergoing a $3B+ transformation to the area, including updates to the arena.
SAP Center in San Jose: not discussing renovations or new arena.
Enterprise Center in St. Louis: underwent $150M renovations completed in 2019.
United Center in Chicago: undergone extensive expansions + renovations since 2008.
Rogers Arena in Vancouver: not discussing renovations or new arena.
TD Garden in Boston: underwent $100M renovation completed in 2019.
Same Age Rinks
Amalie Arena in Tampa: $200M in renovations planned between 2010-2030 as part of lease renewal.
Bell Centre in Montreal: $100M renovations completed in 2018.
Bridgestone Arena in Nashville: $350M in renovations expected over the next 20 years.
Keybank Centre in Buffalo: not discussing renovations or new arena.
Wells Fargo Center in Philadelphia: $400M renovations completed in 2022.
Newer Rinks
Capital One Arena in Washington: undergoing $100M renovations
FLA Live Arena in Florida: not discussing renovations or new arena.
Ball Arena in Colorado: $4B redevelopment proposal of land surrounding arena including arena upgrades
Crypto Arena in LA: $100M+ redevelopment slated for completion in 2024
PNC Arena in Carolina: $225M+ renovations that were planned to start in 2020. Costs likely to be even higher now.
Scotiabank Arena in Toronto: not discussing renovations or new arena.
Nationwide Arena in Columbus: not discussing renovations or new arena.
Xcel Energy Center in Minnesota: not discussing renovations or new arena.
Dallas Stars: Mark Cuban talking about building new arena for Mavericks. Not clear what situation is for Stars, if that's the case.
Newest Arenas
Canada Life Center - Winnipeg - 2004
Prudential Center - New Jersey - 2007
PPG Paints Arena - Pittsburgh - 2010
Rogers Place - Edmonton - 2016
T-Mobile Arena - Las Vegas - 2016
Little Ceasars Arena - Detroit - 2017
UBS Arena - New York - 2021
Mullett Arena - Arizona - 2022*
So, most buildings in the league are either newer or have undergone substantial redevelopment/renovation efforts to modernize. I only found 8 of 32 teams that had no plans for renovations or new buildings. The premise you're presenting is simply incorrect. If old buildings weren't a big concern, then we wouldn't see this kind of money being plowed into older buildings.