Cell hadn't infodumped?

[Captain Cadaver]

Let's say the mystery of his introduction remains such with Cell not completely dropping the ball in telling Piccolo everything and instead said nothing before his retreat. The Z-Warriors have no idea what this creature is or how to combat him. How would events transpire now?

 

[withheldforprivacy]

I can't see any difference. They pursue him unsucessfully for the following days, as in canon. Goku still brings up ROSAT, since the reason he did so in canon is that he and Vegeta sensed that Cell's chi is above unmastered SSJs. When Cell interrupts the fight Piccolo vs Seventeen, everything happens the same way until Cell absorbs Seventeen, which makes everybody realize that Cell absorbs androids, so Eighteen flees.
The only possible difference is that Vegeta does not know about absorptions, so, unless Cell happens to curse as in canon, thus making Vegeta curious to ask what he means, Vegeta just kills Cell. In that case, we have a 'no Buu' scenario (I have described this many times in the past).

 

[Boo Brand Milk]

Let's say the mystery of his introduction remains such with Cell not completely dropping the ball in telling Piccolo everything and instead said nothing before his retreat. The Z-Warriors have no idea what this creature is or how to combat him. How would events transpire now?

Sadly the same, as the Z Warriors never capitalized on the infodump. Also they'd figure out the 'secret' through ki sense anyway.

 

[Captain Cadaver]

What about the fact that the present Cell and Spy Robot would still exist and, aware of the death of the other Cell, wouldn't hesitate in updating their data?

 

[withheldforprivacy]

What about the fact that the present Cell and Spy Robot would still exist and, aware of the death of the other Cell, wouldn't hesitate in updating their data?

So, you think that, after the end of Super, we have a Cell who is SSJ Blue level or above?

 

[Captain Cadaver]

Possibly, depending how much longer Gero uses the Spy Robot for. At the very least, it would make Cell aware of the power he could gain through training like Freeza.

 

[Keedounan]

I doubt this would have changed anything in regards to Future Cell the story, since the Z-Fighters never used this knowledge to their advantage. In fact, Piccolo's fight even led him right to #17 and #18.

Present Cell would have appeared one day and maybe defeat them all, though, as nobody would be aware of his existence.