I remain skeptical that Obi-Wan could know this.I'm pretty sure Anakin would have wanted his son to have that lightsaber though. Its seems like he's nature. The "This weapon is your life" and Anakin taking that to literal sense to show what he felt (handing it to Pandme to show he was serious about her in TCW) It would fit that Anakin would had over "his life" to his children, when they were old enough.
In a way, he did just that, at the end. When he gave his life for his son's life.
Regardless, their is subtext, and then there is reaching text. It doesn't work for me on a number of levels. And, that makes me annoyed as Ewan McGregor is the high point of the PT for me.