What made for me ODST so special was the urban battle. In almost every other halo games we are fighting on some random exotic planet or on forerunner installations. I felt like a real soldier fighting an alien invasion, this is not the feeling i had while playing the other halo games. The game also allowed me to see the covenant war on a different perspective, exploring the humanity on each character and their pain.
I think if they one day make a new ODST game, it will be a side game (like halo 3, it was such a great commercial sucess than they decided 2 years after to make a second opus with the story of the odst troopers during the war [this is the reason why the title is halo 3 ODST and not halo ODST]) and unforthunately, if Halo infinite does not follow the path of the original art and story style, the game will not be as good and special ODST was.
One thing is sure, if they really make a second ODST game, it will probably explore the events of the human / covenant war (most of the odst troops have been converted into Spartan IV after the events of halo 3-4 and the best scenaristic content was from this period).
In my opinion, as Halo 3 Odst already explored the human perspective of the war, ODST should stop there. What could be interesting and ambitious for 343, would be the story of an elite under the charge of Rtas Vadum, fighting the humans, the heretics and the flood during the events of halo 2. A campaign only played by a sangheili with a flood fire fight mod