I must disagree. It is very possible that while "the end" as Pennington so tiredly stated it may indeed be the end - do not discount the very real possibility it won't be the "real" end. Mack has a knack for finding brilliant ways to kill characters off. It's possible that the story - which starts in "real time" in WJC can merely just pick up again - leaving Pennington and Reyes to face some unforeseen drama - leaving them both dead. Pennington did a LOT of homework to FIND Reyes - it's possible his own investigation drudged up people who are also looking to find Reyes - and silence him permanently...
It's a framing story so it has to take place outside the story itself. We are meant to believe that Operation Vanguard is over by the time Pennington tracks down Reyes and asks Reyes about his final time on/near SB47. Then we have the lead-in to Storming Heaven
in which Pennington tells Reyes what happens after Reyes leaves:
'I was there until the end, mate. The bloody, bitter, end.' or words to that effect.
So Pennington is telling that us that he was there when it finally came to end. I don't think there's anything ambiguous in that statement.