No, what Akechi feared now is that Nobunaga's ambition has reached even beyond Japan. Couple dozen chapters back, after the conversation with Valignano, Nobunaga has set his sight to Ming, China, and lands beyond to rub it in the Portuguese face for thinking Japan is just another footnote in their history. With the level of logistics of this time period, waging war in a foreign country is simply impossible even with the backing of an entire nation.

Akechi's fear was that should Nobunaga's campaign on the Ming failed, which it very much will (in actual history, Akechi inherited Nobunaga's dream of conquering Ming after the latter's death, but his force didn't even make it through Korea) then history will only remember him as a tyrant blinded by greed, thus his honor forever smeared, that's why he decided before that happens he will kill Nobunaga in order to retain his honor.

I gues weighed both choices and felt the small chance of victory is too little compared to Oda's name being stained for many decades ahead.

It seems the final chapters are translated and were uploaded today, if you don't want to wait for them to be uploaded here you can look for them online