I think it was rather weak myself. Why would Olympia suddenly get an interest on Frogadier just like that? Why not peek into Serena's, Clemont's, or Bonnie's future while she was at it? It was like Frogadier just got focus just because the power of future sight wanted it.
(Peeking into Ash's future would just spoil who was going to school him hard at the league).
...A broken image?
It was implied that Olympia didn't really have a lot of control over her visions. Most of what she saw was quite vague hence the first apprentice mistaking Ash for being a threat when Olympia said there was a coming threat to the Kalos region that Ash would be caught within the vortex of the threat (and later Team Rocket).
Olympia: I AM OLYMPIA, BETTER KNOWN AS THE LIVING HYPE MACHINE. IN THE FUTURE, I FORESEE ASH'S FROGADIER OBTAINING UNTOLD POWER BEYOND MEASURE!.
Basically yes. Olympia's vision's are plot device to create hype about the upcoming series without giving anything away. Annoyingly so as the wording of the two visions is so vague it makes her look like a backstreet fortune teller. But Olympia never said Frogadire would obtain untold power.
What's interesting however is the wording of Olympia's visions. When she talks about Frogadire's future all she says is "it's power will become greater and greater," and that "it would reach new heights that no one has ever reached before and the two of you will reach them together." This statement is deliberately vague and could refer to just about anything. Both Ash, Clemont and Professor Sycamore had different interpretations. Professor Sycamore asked would it mega evolve, Ash asked would Frogadire become Greninja and Clemont says "a new power nobody's ever seen before is a really big deal." Arguably all three of them are sensationalising and misinterpreting what Olympia is saying. Olympia didn't say Frogadire would either evolve or gain a new power. Olympia never refers to Greninja having a power. All she said was it would reach new heights. She certainly didn't say it will become the Ash Greninja and have a power comparable to mega evolution, which is what the Ash Greninja is supposed to be.
It's hard to see how people get "untold power" from the statement "reach new heights," and "reach them together." This actually sounds more like an external achievement, like winning the league, rather than Frogadire gaining a special power within it's self. She also says Frogadire was looking for love when it chose Ash - That implies reach new heights and reach them together could mean something vastly different from special evolutions or league victories
The first vision is even worse as she refers to a coming disaster, people who will gather in Anistar City who be at the vortex of it, something about a green eye and those lead by it at which point she shows a picture of Ash and Pikachu (Ash's eyes are brown), and the one who will show the the way which is accompanied by a picture of Professor Sycamore. This is probably supposed to refer to Team Flare's appearance in the series but it's so vague it's actually meaningless. All we know is something bad will happen that Ash and Pikachu will be caught in. It could mean anything.
Personally I thought Olympia came across as a bit of con-artist. She used mysticism and showmanship to impress everybody and make them believe she could see the future. But when you actually think about her "visions" she didn't give any concrete detail about what was going to happen. Obliviously there's a reason it was drafted this way. Essentially what the episode is trying to do is create a hype for the XYZ arch without actually saying what's going to happen or what it will be about. In terms of cannon we can probably assume the visions are genuine.
I'll give it 7/10
At least no Pikachu glorification.
That's a pity. Pikachu hasn't had a moment to shine since the 5th gym and if Olympia is referring to XYZ it would be nice to give Pikachu the spotlight. They did in episode N and the climax of Team Aqua and Team Magma's arch. Also it's reasonable to presume Pikachu's important in someway given he does appear in Olympia's first vision (frogadire doesn't appear there). Olympia does mention love a couple of times which would apply more to Pikachu than Frogadire.
And by the way, it's common knowledge Ash Ketchum will lose at the league as always.
You don't need to be psychic to predict that!
. 
