If they call it Xbox anything, the console will be automatically associated with previous Xbox consoles. Usually it's associated with the most recent one and recent years because the memory is still fresh. In Japan the Xbox name has the reputation of redundancy. It's similar in mainland Europe where gamers prefer to stick to their PCs, so Microsoft's initiative to support Xbox and PC equally won't help matters. For those who want a console, PS is the prefered option because that style of games has established itself before the arrival of the original Xbox and the only way to break that up for Xbox is to be a significantly superior alternative to PS, hence why the 360 managed to do reasonably well in mainland Europe unlike other Xbox consoles.
If Microsoft calls their next console Xbox, they'll have to hope for Sony making mistakes with the PS5, otherwise their situation in mainland Europe won't improve due to the association and perception the Xbox brand has. "Same old Xbox" won't cut it.
That's why it shouldn't be the "same old Xbox", it should improve over past consoles by not having either Xbone's crippling early mistakes or 360's reliability issues. A next gen Xbox that doesn't suffer from any such serious problems and is well designed and marketed could beat PS in America and do better overseas than Xbone.
It probably won't outsell Playstation 5 globally, but it doesn't have to to still be a profitable and worthwhile venture.