I personally don't think Halo5 will be 100% ready by launch. I feel Microsoft will rush it out to take advantage of the holiday season. I hope I am wrong but the development cycle just seems too short for a mainline next-gen Halo game considering Halo 4 only came out in 2012... 3 year cycle.... This isn't like Halo 1 and2 where it was on the same console or Halo 3 and ODST...
You're talking about a 300 dev strong team that have engineers that have worked on the console, devs (especially bosses) that have been working on Halo since CE, they released a Beta a year out running butter "smoov". Snags always happen but I beliebe 343i is the best suited dev team to work on X1.
Time will tell.
You're not giving very good reasons for your skepticism.