Asking a colleague for his submitted paper

If he is a colleague, he is unlikely to think that. Just express your interest and ask for an early look. If something in it seems interesting to you contact him again and see if you have the possibility of collaboration on an extension or similar work.

It is how collaborative relationships get formed. Just do it.

Just ask him or her. I’m not sure how you can steal the ideas of someone who will make a public presentation on these ideas. Moreover, your colleague presumably has proof that has submitted this so there can no issue as to priority.