It might indicate that, reading into everything he has done for her.
However, I think the whole relationship is meant to show her as his 'IMF Child' if you will. He trained her, and respected her enough to recommend her. While, in context, this could be taken as romantic. I think it was so much more than that for him which is why he went on this giant ...
Benji Dunn: According to one of these e-mails, your Mr.Davian is going to attend a function in tomorrow afternoon at one Vatican City.
Luther: What the hell's Davian doing in Vatican?
Benji: Well, it's all got to do with "the Rabbit's foot".
Ethan: What is that?
Benji: I'm assuming it is a kind of code-word for a deadly weapon, something ...
It's a biohazard, that means
something that may cause harm to people or to the environment, especially a poisonous chemical or an infectious disease
Here, this picture confirms that Rabbit's foot is a biohazard.
Just to add on and add some sources and additional things to consider:
First we don't have enough information to know for certain what the true nature of Ethan's and Lindsay's relationship was, but given that Ethan Hunt is a traditional protagonist and is probably viewed as an honorable man, we may assume that he means what he says, when he tells Luther, ...