Aeris' face at the end is a deliberate bit of parallelism to the opening scene.

I think its meant to remind the viewer that she is responsible for the Lifestream's arrival in hte time of need.

As for meeting her at the Promised Land... Cloud finally began to understand the connection between the Cetra and the Planet, so I think he realised that it'd be possible to 'meet' Aeris, on a spiritual level at least - perhaps by going to someplace where the Lifestream was active and accessible.