As of Q2 2026, Adobe positioned the new 'Build with AI' interface as complementary to the classic Marketo UI — not a replacement. There is no announced deprecation date. Admins can decide, per user, which interface they see. That is the good news.
The other news: every new feature Adobe has released in 2026 — agent skills, Email Designer Brand Management, the Program Planning agent, the Build with AI conversational layer — lives in the new interface. Staying on classic indefinitely means opting out of the roadmap.
The strategic question: when, not whether
Most teams should plan a phased migration inside 12 months, not because they are forced to, but because the training and governance investment is easier absorbed in one project than in five surprises.
The three phases we run
Phase 1 — Low-risk pilot
Pick one or two low-stakes programs (internal comms, employee welcome, or a dormant nurture) and rebuild them in the new UI. Do not migrate high-traffic campaigns first. The goal is to surface friction — for the team, not for the customers — before it costs real send volume.
Phase 2 — Template Import for medium-complexity assets
For higher-impact but moderate-complexity emails, use Template Import rather than rebuilding from scratch. This preserves your existing HTML while placing the asset into the new module/structure model. You will still need to review the imported template for Brand Theme conformance and for locked-content decisions.
Phase 3 — Cohort rollout with parallel sends
Shift users cohort by cohort. For any critical program, run a parallel send from the new UI and the classic UI on separate audience samples for one to two full cycles. Compare opens, clicks, bounces, and rendering. Only cut over the campaign once the parallel run matches.
What to write down before you start
- Template inventory — which templates are in daily use, monthly use, and effectively dead.
- Approved brand values — fonts, colors, spacing, allowed image sources. These become the Brand Theme.
- Content-locking decisions — which fields any marketer can edit, which are locked to MOPs.
- Fragment plan — the four to eight blocks (footer, legal, standard header, product footer, etc.) that should become Fragments day one.
- Rollback plan — keep the classic version inactive but retained for at least two cycles.
What to expect on the way
Early adopters of the new Email Designer through 2025 reported real friction — feature parity gaps, tooling incompatibilities, some rendering surprises. By late 2025 and into 2026 the platform has stabilized substantially, and most of the feature-parity items on the community wishlist have shipped or are on the near roadmap. Segment-based dynamic content and custom fonts remain the two most-cited outstanding gaps.
“Migration is not the risk. Migration without a template inventory, a brand theme, and a rollback plan is the risk.”
Where classic still wins today
For a handful of workflows — complex HTML-first templates, some heavily-tokenized transactional patterns, and workflows involving third-party editors that have not yet integrated with the new designer — classic remains the safer choice through 2026. Adobe has repeatedly stated the classic UI stays available; use that runway to migrate deliberately.
If your team is planning a migration and wants a written phased plan with owners, dates, and rollback triggers, this is exactly the sort of engagement Xadentra runs.