Let's say we get to a point as a species that we are fully integrated with one another in some sort of post singularity grid.

One could perhaps call it a... global brain.

We have access to all information and data at all times.

MMmMmMMmmm... all the information in our brainssszzzz...

Do you think this eliminates a sense of self?

I think higher types of consciousness will start to emerge. I still think you will have your own consciousness. But discussions between different collections of "people" will include mergers of "brain spaces", Ben Goertzel has called them "mindspheres". The best way to imagine this is by comparing your state of consciousness when you're alone to when you are a room full of people having a conversation. Your consciousness (or state of mind) is much different in these two situations... you might even say that there is a "feeling" in the room... a collection of the feelings/thoughts of all those taking part in the conversation. However, with digital minds that conversation could take place without language... we could actually subjectively feel each others thought patterns, or collection of thought patterns of multiple people. This would be a qualitatively different type of experience than the types of conversations we have today... just like explaining language to an australopithecine would be impossible... explaining this completely may be impossible.

Will we all have the same conclusions?

I highly doubt it (because I think information and knowledge are different things - and having the same information doesn't mean having the same opinion about that information), although I feel like our collective opinions will get closer and closer. You can imagine this with a simple thought experiment. Imagine we were to have four people from 1500 (say from Europe, Africa, Asia and Australia) magically teleported into the same room and forced to discuss their thoughts on the world. If they could eventually understand each other, their opinions on reality would undoubtedly be radical divergent. If we continually ran this experiment every century (i..e, 1600, 1700, 1800, 1900, 2000, and so on) our global conversation would be becoming more and more coherent with more and more agreement and less and less disagreement. This would just be a function of globalization and the rate of cultural information transfer in the system. We should expect this to continue - but I doubt it will continue to the point where all agents in our collective global brain system agree on everything. I think we will largely have discarded with notions connected to our hunter-gatherer and agricultural past, but we will still disagree about bleeding edge scientific theory or perhaps even spirituality.